The present invention relates to two stage speed reducers and, more particularly, to such reducers having a primary reduction stage, the output gear of which provides the drive for the output or secondary stage which consists of an eccentric, an output planetary gear and a fixed ring gear.
Eccentric planetary drives are well known in the art, as typified by one or more of the following prior patents:
1. U.S. Pat. No. 3,037,400 discloses a two stage reducer wherein an eccentric drives, through bearings, a stepped pinion which mates with a stationary ring gear and an output ring gear.
2. U.S. Pat. No. 3,939,737 discloses an arrangement wherein a stepped pinion is eccentrically driven by an input shaft, through bearings, for engagement with a fixed ring gear and an output ring gear.
3. U.S. Pat. No. 4,235,129 discloses an arrangement wherein the hub of an input pulley is the eccentric for driving a floating pinion that coacts with an output ring gear. The eccentric hub forms the inner race for the bearings which permit rotation of the floating pinion.
4. U.S. Pat. No. 4,155,276 discloses an arrangement wherein first and second stage spur gears are driven by eccentric ring gears.
5. U.S. Pat. No. 3,602,070 discloses an arrangement wherein orbital movement of a floating gear is accomplished by planetary rollers or gears of different sizes.